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UNLESS you have a TH400 3 speed HD automatic transmission, which I HIGHLY doubt being it's a 1500 with a 4.3, you won't have a vacuum modulator. UNLESS someone swapped an older TH350 or TH400 transmission into the truck.
Instead you'll have what called a TV cable, or throttled valve cable.
This cable should be located on the passenger side of the transmission and is routed up to the side of the throttle body and hooked up like the old "kick down" cables.
The TV cable isn't simply a "kick down" cable, even though it does act like one, it also adjusts the pressure for the transmission to shift at different throttle positions. Much like the old vacuum modulators did.
under hood look where the throttle cable connects behind it u will see a black looking module thats the throttle sensor the idle control is located just to the rite toward the filter as the mass sensor is there too
Older Model Computer Codes (OBDI) - IMPORTANT! Codes may be different for newer vehicles starting circa 1996.
11 No ignition reference signal detected during cranking OR timing belt
skipped one or more teeth; OR loss of either camshaft or crankshaft
12 Battery or computer recently disconnected
13 MAP sensor or vacuum line may not be working
14 MAP sensor voltage below .16V or over 4.96V
15 No speed/distance sensor signal
16 Loss of battery voltage detected with engine running
17 Engine stays cool too long (bad thermostat or coolant sensor?)
17 (1985 turbo only): knock sensor circuit
21 Oxygen sensor signal doesn't change (stays at 4.3-4.5V). Probably bad oxygen sensor
22 Coolant sensor signal out of range - May have been disconnected to set timing
23 Incoming air temperature sensor may be bad
24 Throttle position sensor over 4.96V
25 Automatic Idle Speed (AIS) motor driver circuit shorted or target idle not reached
26 Peak injector circuit voltage has not been reached (need to check computer signals, voltage reg, injectors)
27 Injector circuit isn't switching when it's told to (TBI)
OR (MPI) injector circuit #1 not switching right
OR (turbo) injector circuit #2 not switching right
OR (all 1990-) injector output driver not responding
- check computer, connections
31 Bad evaporator purge solenoid circuit or driver
32 (1984 only) power loss/limited lamp or circuit
32 EGR gases not working (1988) - check vacuum, valve
32 (1990-92) computer didn't see change in air/'fuel ratio when EGR activated - check valve, vacuum lines, and EGR electrical
33 Air conditioning clutch relay circuit open or shorted (may be in the
wide-open-throttle cutoff circuit or normal on early 80's models if you
don't have air conditioning)
34 (1984-86) EGR solenoid circuit shorted or open
34 (1987-1991) speed control shorted or open
35 Cooling fan relay circuit open or shorted
35 idle switch motor fault - check connections
36 (turbo only) Wastegate control circuit open or shorted
37 Shift indicator light failure, 5-speed
part throttle lock/unlock solenoid driver circuit (87-89)
solenoid coil circuit (85-87 Turbo only)
Trans temperature sensor voltage low (1995 and on)
41 Alternator field control circuit open or shorted
42 Automatic shutdown relay circuit open or shorted
42 Fuel pump relay control circuit
42 Fuel level unit - no change over miles
42 Z1 voltage missing when autoshutdown circuit energized (The Z1
voltage is the voltage of the circuits fed by the autoshutdown relay.
This typically includes fuel pump and switched-battery feed to the
43 Peak primary coil current not achieved with max dwell time
43 Cylinder misfire
43 Problem in power module to logic module interface
44 No FJ2 voltage present at logic board
44 Logic module self-diagnostics indicate problem
44 Battery temperature out of range
45 Turbo boost limit exceeded (engine was shut down by logic module)
46 Battery voltage too high during charging or charging system voltage too low
47 Battery voltage too low and alternator output too low
51 Oxygen sensor stuck at lean position (this may be tripped by a bad
MAP sensor system causing a rich condition. If you get hot rough idle
and stalling, especially on deceleration, accompanied by flooded engine
and difficulty restarting, that can be a bad MAP sensor causing the O2
sensor to try to compensate. If you get poor cold driveability,
stumbling and bucking, and acceptable warm driving with poor gas mileage
(a drop of 10 mpg or more), that is usually the O2 sensor.
51 Internal logic module fault ('84 turbo only).
52 Oxygen sensor stuck at rich position
52 Internal logic module fault ('84 turbo only)
53 Logic module internal problem
54 No sync pickup signal during engine rotation (turbo only)
54 Internal logic module fault ('84 turbo only) - or camshaft sensor/distributor timing
55 End of codes
61 "Baro" sensor open or shorted
62 EMR mileage cannot be stored in EEPROM
62 PCM failure SRI mile not stored
63 Controller cannot write to EEPROM
64 Catalytic converter efficiency failure
65 Power steering switch failure
66 No CCD Message From TCM and/or No CCD Message From BCM
• Powertrain Control Module Description for the 2.8L engine
• Powertrain Control Module Description for the 3.5L engine
Throttle Actuator Control (TAC) System
Throttle Actuator Control (TAC) Overview
The throttle actuator control (TAC) system uses vehicle electronics and components to calculate and control the position of the throttle blade. This eliminates the need for a mechanical cable attachment from the accelerator pedal to the throttle body. This system also performs the cruise control functions as well.
The TAC system components include, but are not limited to the following:
• The accelerator pedal position (APP) sensors
• The throttle body
• The powertrain control module (PCM)
Each of these components interface together to ensure accurate calculations and control of the throttle position.
Accelerator Pedal Position (APP) Sensor
The accelerator pedal position (APP) sensor is mounted on the accelerator pedal assembly. The APP is 2 individual APP sensors within one housing. There are 2 separate signal, low reference, and 5-volt reference circuits. APP sensor 1 voltage increases as the accelerator pedal is depressed. APP sensor 2 voltage decreases as the accelerator pedal is depressed.
Throttle Body Assembly
The throttle body for the throttle actuator control (TAC) system is similar to a conventional throttle body with several exceptions. One exception being the use of a motor to control the throttle position instead of a mechanical cable. Another exception is the throttle position (TP) sensor. The TP sensor is mounted in the throttle body assembly. The TP sensor is 2 individual TP sensors within the throttle body assembly. Two separate signals, low reference, and 5-volt reference circuits are used to connect the TP sensors and the powertrain control module (PCM). TP sensor 2 signal voltage increases as the throttle opens. TP sensor 1 signal voltage decreases as the throttle opens.
Reduced Engine Power Mode
When the PCM detects a problem with the throttle actuator control (TAC) system the PCM enters one of the following Reduced Engine Power Modes:
• Acceleration Limiting--The control module will continue to use the accelerator pedal for throttle control, however the vehicle acceleration is limited.
• Limited Throttle Mode--The control module will continue to use the accelerator pedal for throttle control, however the maximum throttle opening is limited.
• Throttle Default Mode--The control module will turn OFF the throttle actuator.
• Forced Idle Mode--The control module will perform the following actions:
- Limit engine speed to idle by positioning throttle position, or by controlling fuel and spark if throttle is turned OFF.
- Ignore accelerator pedal input.
• Engine Shutdown Mode--The control module will disable fuel and de-energize the throttle actuator.
Have you had it checked for DTC'S - diagnostic trouble codes ?
The commanded throttle position (TP) is compared to the actual TP. Both values should be within a calibrated range of each other. The powertrain control module (PCM) continuously monitors the commanded and actual TPs. If the values are greater than the calibrated range, DTC P2176 sets.
The accelerator pedal position (APP) sensors 1 and 2 are located within the accelerator pedal assembly. Each sensor has the following circuits:
• A 5-volt reference circuit
• A low reference circuit
• A signal circuit
This provides the powertrain control module (PCM) with a signal voltage proportional to accelerator pedal movement. The APP sensor 1 signal voltage at rest position is near the low reference and increases as the pedal is actuated. The APP sensor 2 signal voltage at rest position is near the 5-volt reference and decreases as the pedal is actuated.
The throttle actuator control (TAC) assembly has 2 throttle position (TP) sensors mounted within the assembly. The powertrain control module (PCM) provides individual signal, ground, and 5-volt reference circuits to each sensor. Both sensors operate within a voltage range between 0.35-4.65 volts. When the throttle is opened from 0-100 percent, one sensor signal voltage increases while the other decreases. The signal circuit for TP sensor 1 is referenced to ground, and the signal circuit for TP sensor 2 is pulled up to 5 volts within the PCM.
Hi there: Definetivelly you have a problem with emission and injection syste,, check this code descriptions...
DTC 13 - MAP (Manifold Absolute Pressure) sensor pneumatic failure: sensor output does not change Power loss light: On Limp-in mode: TPS and engine speed used as an indication of manifold pressure
Possible Causes: Broken or disconnected vaccum line - Check the vaccum line leading from the MAP sensor. On '87 and later engines, the sensor is located on the right shock tower and the vaccum line often gets pulled or pushed off. Replace the entire line with a piece of 1/8" I.D. vaccum hose making sure to provide enough slack in the line.
Bad Baro-read solenoid - The barometric read solenoid may not be operating. Try bypassing the solenoid, connecting the MAP sensor directly to the manifold to see if the engine runs better (this may not prevent the code 13, however). If not accompanied by a code 37, you can try to repair or replace the solenoid. See the Understanding Solenoids page for information about how to test and repair solenoids.
Moisture in MAP sensor - If this mostly occurs old cold weather, then you may have water that is freezing inside the sensor. This is a common problem on vehicles that have the sensor located on the logic module. Remove the sensor and bring inside to warm up. Shake any droplets out of the sensor and set it in a warm, dry place for a day or so. Don't try to take the sensor apart because you may destroy it. Check all your vaccum lines because a vaccum leak would be the most likely cause of water entering the system. If your MAP sensor is located on or near the logic module, you may wish to consider moving it under the hood on the right shock tower. All 1987 and later models were set up this way to prevent moisture collection in the MAP sensor.
Pinhole leak in Fuel Pressure Regulator - Occasionally, a small leak will develop in the fuel pressure regulator diaphram that allows fuel to enter the vacuum system. This upsets the response of the vacuum system, triggering this code. Check for the presence of fuel in the vacuum line to the fuel pressure regulator. If fuel is present, replace the regulator.
MAP sensor failure - A bad MAP sensor will usually cause a code 14, so this is not as likely to be the cause of a code 13. But if it comes down to it, replace the MAP sensor which is located on the right shock tower on '87 and later vehicles or in the logic module on previous vehicles. Damage from freezing water can destroy a MAP sensor.
DTC 16 - Loss of battery voltage detected with engine running Power loss light: On Limp-in mode: 25% alternator field coil duty cycle
Possible Causes: Blown fusible link to power module (or SMEC) - Check the only white fusible link (may look grey if dirty) by tugging on it. A good link will feel solid while a blown link will stretch like a rubber band. It is the white link on the two-link circuit (not the four or five link circuit). This link supplies power to the ASD relay and the voltage sense input on the logic module (may be accompanied by a code 42). See the Fusible Links page for more details.
Bad connection or wiring - Check the wiring and connections between the alternator and the battery, power module and the alternator field coil, and the voltage sense line through the power and logic modules.
Alternator failure or bad voltage regulator circuit - See the Diagnosing Your Charging System page.
Diagnostic Method Trigger Parameters - 60 seconds after engine startup - Voltage sense input is below 8.5V Results If Component Fails If the voltage sense input is between 4V and 8.5V, the logic module will full-field (100% duty cycle) the alternator field coil for 20 seconds. If the voltage sense input is still below 8.5V, the system enters limp-in mode, the power loss light is turned on, a fault code 16 is stored, and the alternator field coil driver will enter a fixed, 25% duty cycle.
If the voltage sense input is below 4V, the system enters limp-in mode, the power loss light is turned on, and a fault code 16 is stored. The alternator field coil driver will enter a fixed, 25% duty cycle to prevent overcharging of the battery, but allow the vehicle to operate.
DTC 24 - Throttle position sensor (TPS) signal is out of range Power loss light: On Limp-in mode: MAP sensor is used as an indication of thottle position
Possible Causes TPS failure - The TPS is located on the throttle body on the opposite side of the throttle cable. Turn the engine off, disconnect the sensor and test it by connecting an ohmmeter (preferably an analog one) between the center and either outside pin of the sensor. Slowly open the throttle all the way and then slowly close it again. The ohmmeter should show a constant, smooth change in resistance as the throttle is moved. If there are any jumps in reading or no change in reading at all, replace the sensor. If the sensor seems ok, reconnect the sensor cable and turn the ignition on. One outside wire should be 5V, the other ground. The voltage on the center wire should vary as the throttle is opened (about 0V closed, 3V wide open). If power or ground is not present, check the wiring.
Bad connection or wiring - Check the wiring and connections between the sensor and the logic module (or SMEC). Clean and regrease any corroded connectors with dielectric grease. Check connections if there is no power or ground, or for shorts if there is power and resistance, but no output.
Diagnostic Method Trigger Parameters - Sensor output less than 0.16V or greater than 4.7V Results If Component Fails Fault code 24 is stored, the power loss light is turned on, and the logic module will enter limp-in mode. The logic module will then use the MAP sensor as an indication of the thottle position. A MAP sensor voltage less than 2.0V is considered closed throttle and a MAP sensor voltage greater than 2.0V is considered wide open throttle (WOT).
DTC 27 - Injector driver circuit 2 open or shorted Power loss light: Off Limp-in mode: None
Possible Causes Bad connection or wiring - Check the wiring and connections to injectors 3 and 4 in the injector harness (above the fuel rail) and between the harness and the power module (or SMEC) and the injector contol lines between the logic module and power module. Clean and regrease any corroded connectors with dielectric grease and repair any shorts.
Injector driver transistor failure - Check the injector signals coming from the power module (or SMEC). They should rise to about 12V when the injector is off and drop close to 0V when the injector is on. If they are out of spec, you may need to replace the power module.
Diagnostic Method Trigger Parameters - Near 0V or near 12V not detected when the injector driver is turned on or off, respectively Results If Component Fails Fault code 27 is stored.
DTC 36 - For MPI N/A engines
Description: Air switching solenoid circuit is open or shorted Power loss light: Off Limp-in mode: None
Possible Causes Bad connection or wiring - Check the wiring and connections between the logic module and the solenoid. Clean and regrease any corroded connectors with dielectric grease and repair any shorts.
Bad solenoid - The solenoid is located in the right, front fender next to one to three other solenoids. See the Understanding Solenoids page for information about how to test and repair solenoids.
Diagnostic Method Trigger Parameters - Near 0V or near 12V not detected when the solenoid is turned on or off, respectively Results If Component Fails Fault code 36 is stored.
DTC 51 - Oxygen sensor output indicates lean too long Power loss light: Off Limp-in mode: Engine allowed to run rich, but prevented from running lean
Possible Causes Bad oxygen sensor - Replace the sensor which is located on the turbo housing near the down pipe (for turbo) or on the down pipe near the exhaust manifold.
Bad connection or wiring - Check the wiring and connections between the sensor and the logic module (or SMEC). Clean and regrease any corroded connectors with dielectric grease and repair any shorts. Look for melted wire insulation near the exhaust manifold. A shorted connection to ground or any positive source will cause this fault code.
Low fuel rail pressure - See the Diagnosing Your Fuel System page.
Diagnostic Method Trigger Parameters - In closed-loop - Sensor output indicates lean for more than 715 seconds (11 minutes, 55 seconds) Results If Component Fails A fault code 51 is stored, the circuit stays in closed-loop, and the logic module will still monitor the oxygen sensor signal. If the condition persists for four times what it took to set the code, the logic module will allow the engine to run rich, but prevent it from running lean.
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Code 11 Description: Engine not cranked since last reset or no ignition reference signal detected during cranking Power loss light: Off Limp-in mode: None
Possible Causes: Engine hasn't been cranked since last reset - Power was removed from the logic module (disconnected or dead battery, etc.) and the logic module has no memory of seeing a signal from the ignition reference sensor. Crank the engine and check for the code again. If the logic module saw a signal, the code will be cleared. This code will not show up if the sensor simply fails. The logic module must be reset and the engine cranked to see if the sensor is working.
Bad connection or wiring - Check the wiring and connections between the hall effect sensor (located underneath the distributer cap) and the logic module. Check the continuity of the two 3 conductor cables coming out of the sensor--these are prone to fatiguing and breaking inside the insulation where they exit the sensor if the cables are not properly tied down. You may be able to resolder them. Clean and regrease any corroded connectors with dielectric grease and repair any shorts. This code will not show up if the sensor simply fails. The logic module must be reset and the engine cranked to see if the sensor is working (see above).
Hall effect sensor failure- Check the ignition reference sensor and fuel injector sync sensor cables. They are the two, flat 3 conductor cables coming out of the sensor at the base of the distributer cap. These often fatigue where they exit from the sensor. Upon replacing the sensor, make sure the cables are clipped or tied to the distributor cap shroud (or elsewhere) so they do not swing around. This code will not show up if the sensor simply fails. The logic module must be reset and the engine cranked to see if the sensor is working (see above).
Code 23 Notes: For throttle body injected (N/A) models only
Description: Throttle body temperature sensor signal out of range Power loss light: On Limp-in mode: Throttle body temperature of 70^F is assumed
Possible Causes Throttle body temperature sensor failure - The sensor should measure 9,120 ohms to 10,880 ohms at 77^F. This sensor is located on the side of the throttle body, below the throttle plate.
Bad connection or wiring - Check the wiring and connections between the sensor and the logic module (or SMEC). Clean and regrease any corroded connectors with dielectric grease.
Diagnostic Method Trigger Parameters - Sensor output less than 0.06V or greater than 4.98V Results If Component Fails Fault code 23 is stored, the power loss light is turned on, and the logic module will enter limp-in mode, assuming a throttle body temperature of 70^F.
Code 32 Description: Logic module did not see a change in air/fuel ratio when EGR circuit was activated Power loss light: Off Limp-in mode: None
Possible Causes EGR valve stuck open or closed - If the vehicle fails emmisions, then the valve may be shut. If the enigne runs poorly at low rpm or at idle, the valve may be stuck open. It may be the valve or the transducer valve. Test the transducer valve vacuum output. At idle, the transducer valve vacuum should be mostly bled, and there should be very little, if any vacuum at the output. When the engine is revved, the vacuum should increase. If the transducer is functioning properly, replace the EGR valve.
Bad EGR solenoid or Canister purge/EGR solenoid - The solenoid is located in the right, front fender next to one to three other solenoids. See the Understanding Solenoids page for information about how to test and repair solenoids.
Bad connection or wiring - Check the wiring and connections between the solenoid and the logic module (or SMEC). Clean and regrease any corroded connectors with dielectric grease and repair any shorts.
Diagnostic Method Trigger Parameters - The EGR solenoid was deactivated, but the oxygen sensor reading did not change Results If Component Fails Fault code 32 is stored.
Code 55 Description: End of message Power loss light: Off Limp-in mode: None
Possible Causes No further fault codes are stored. If this is the only code received, then there are no codes stored in memory. This code will always be given, even if nothing is wrong. If you do not get this code, then you may not be retreiving the codes properly, or the power loss light may be burnt out. The light should come on for 1 second when the ignition is initally turned on as a bulb test.
Diagnostic Method Trigger Parameters - No further codes in memory